How can I be a better writer?

I apologize for my ignorance. I am catholic and enjoy writing stories. One I have gotten particularly attached to and wish to publish.

One of my characters is Greek Orthodox, and I would like to know what is some common misconceptions when people do write Greek Orthodox characters or what can I do to make the character more believable? I don't want to misinterpret the religion. I am doing as much as I can to research but I'd also like physical feedback.

Once again, I apologize for my ignorance, I am Catholic but trying to include many different religions in my works.